The Micro Four Thirds System standard maintains the Four Thirds System concept of "High-picture quality digital-dedicated design," but focuses on reducing overall system thickness and size by aiming for a highly portable compact system.

The Micro Four Thirds System also embodies our ongoing efforts to expand the Four Thirds System-based standards to meet future needs such as movie compatibility, to improve the comfort of Live View shooting and to increase the usability of existing Four Thirds System interchangeable lenses.

The biggest attraction of any SLR camera system is the ability to change lenses. However, if the imaging plane (focal point) varies depending on the angle of view or focal length of each lens, it would not even be possible to focus the subject. To avoid this problem, the imaging plane of all interchangeable lenses is standardized by strictly specifying the length of the flange back, or the distance from the mount plane to the film/image sensor surface.
Digital SLR cameras incorporate more components between the lens and the image sensing material than film SLR cameras, such as the image stabilizer, dust reduction mechanism and low-pass filter. Also, since the viewfinder of an SLR camera requires a mirror box for viewing the real image, the flange back needs to be longer to accommodate the mirror box. Compact cameras do not use the mirror box, so don't require a long flange back. These factors have made it difficult to design SLR cameras that are as slim and compact as compact cameras.
However, if a digital SLR camera can be designed to exclusively use Live View for shooting, the mirror box is no longer necessary and the camera can be designed with the kind of slim profile previously considered impossible, without compromising the high picture quality. For example, when an ultra-slim pancake lens is combined with the camera, it can be stored and taken out of the inner pocket of a jacket, allowing the user to benefit from the high picture quality of SLR with a higher degree of freedom.
The Micro Four Thirds System is a new standard based on combining Live View shooting with the Four Thirds System, freeing users from the viewfinder and moving closer to an optimum balance between picture quality and compact size. With the Micro Four Thirds System, more people will be able to enjoy the excitement of interchangeable lenses and system extension capabilities that only SLR photography can offer, while still benefiting from the convenience and high portability of ordinary fixed-lens compact cameras.

The benefits of reducing the size of an interchangeable-lens type camera cannot be properly experienced unless the size of the lens itself is reduced as well as that of the body.
Therefore, the Micro Four Thirds System standard has reduced the outer diameter of the lens mount to enable lens size reduction.
The new lens mount diameter is about 6 mm smaller than before because this size allows the mount to transmit the same optical flux to the Four Thirds System while still retaining the required strength.
In addition, the lens mount of the Micro Four Thirds System is equipped with two additional signal contacts for smoother Live View shooting with shorter time lags, faster higher communication speeds between the lens and body, and, of course, reduced lens and camera size.
These two contacts will also be used in high-speed data processing required for the movie handling capability expected in the future.

Wouldn't it be something if a single camera the size of highly portable compact camera could record both still images and movies with the high picture quality befitting an SLR?
This dream can become reality with the Micro Four Thirds System standard.
Soon users will be able to switch easily between shooting still images and movies using natural, intuitive operations while keeping the useful Live View on the monitor screen.

To make full use of the advantages of size reduction and new functions of the Micro Four Thirds System standard, it is necessary to combine a dedicated Micro Four Thirds System lens with the body. But existing lenses compliant to the Four Thirds System standard can also be used by attaching a dedicated adapter.

* When a Four Thirds lens is mounted on a Micro Four Thirds body using an adapter, all of the functions of the Micro Four Thirds System may not always be available.